Pop-up irrigation sprinklers are typically buried in the ground and include a stationary housing and a riser assembly mounted within the housing that cycles up and down during an irrigation cycle. During irrigation, pressurized water typically causes the riser assembly to elevate through an open upper end of the housing and rise above the ground level to distribute water to surrounding terrain. The pressurized water causes the riser assembly to travel upwards against the bias of a spring to the elevated spraying position to distribute water to surrounding terrain through one or more spray nozzles. When the irrigation cycle is completed, the pressurized water supply is shut off and the riser is spring-retracted back into the stationary housing.
A rotary irrigation sprinkler commonly includes a rotatable nozzle turret mounted at the upper end of the riser assembly. The turret includes one or more spray nozzles for distributing water and is rotated through an adjustable arcuate water distribution pattern. Rotary sprinklers commonly include a water-driven motor to transfer energy of the incoming water into a source of power to rotate the turret. One common mechanism uses a water-driven turbine and a gear reduction system to convert the high speed rotation of the turbine into relatively low speed turret rotation. During normal operation, the turret rotates to distribute water outwardly over surrounding terrain in an arcuate pattern.
Rotary sprinklers may also employ arc adjustment mechanisms to change the relative arcuate distance between two stops that define the limits of rotation for the turret. One stop is commonly fixed with respect to the turret while the second stop can be selectively moved arcuately relative to the turret to increase or decrease the desired arc of coverage. The drive motor may employ a tripping tab that engages the stops and shifts the direction of rotation to oscillate the turret in opposite rotary directions in order to distribute water of the designated arc defined by the stops.
There are also rotary sprinklers that can select either part-circle rotation of the turret or full-circle rotation of the turret. In the full-circle rotation mode, the turret does not oscillate between the stops, but simply rotates a full 360° without reversing operation. Such selectable rotary sprinklers generally employ a switching mechanism that decouples the reversing mechanism from the stops. For example, some types of switchable rotors shift the arc stops to a position that does not engage the tripping tab. Such designs have the shortcoming that the adjustable stops need to be constructed for both radial adjustment for part-circle operation and also for adjustment in some additional manner in order to avoid the tripping tab. These designs are also less desirable because, in many cases, the part-circle settings of the arc stops may need to be re-established each time the sprinkler is shifted back to part-circle operation.
Other types of switchable sprinklers rely on mechanisms that allow either the arc stops or trip tab to cam around each other due to the stop or tab being resiliently bent. These types of configurations are less robust because the camming component can wear out over time as a result of its repeated bending during full-circle operation. In addition, the camming engagement of the trip tab and/or arc stops during full-circle operation may also cause some unintended movement of the arc stops, which could affect the arc of watering once the sprinkler is shifted back into part-circle mode and require resetting of the desired arc stop locations.
Yet other types of switchable sprinklers employ mechanisms that separate the shifting device from the arc stops, but still allow the stops to engage the tripping tab during operation. These configurations are also less desirable due to the added stress imparted to the tripping tab because it is always engageable with the arc stops in both a full-circle and a part-circle mode. In each prior case, the intricacy of these prior devices renders such sprinkler configurations overly complex, difficult to manufacture, and with many parts potentially prone to wear and tear over time. Also, due to the engagement of the arc stops and tripping tab even during full-circle operation, such prior designs may also require additional re-adjustment of the sprinkler when selecting the part-circle operation after watering in a full-circle mode due to unintended shifting of the arc stops through the continued engagement with the trip tab.